Process of making asphaltic road material



I 1,620 813 Much 1927' J. D. FORRESTER PROCESS OF MAKING ASPHALTIC ROAD MATERIAL Filed Nov. 1925 v INVENTOR.

vii/124's: I

v ATTOI EY.

Patented Mar. 15, 1927.

UNITED 'srarias 1,620,813 PAT T; OFFICE.

JOHN D. FQRRESTEB, OF KANSAS CITY, MIS SOURI, A SSIGNOR To PETER J. MOINERNEY,

7 OF DALLAS, TEXAS.

'rnocnss or MAKING AsrH'AL'rIc noAb MLTERTAL.

ap lication filed November 30, 1925. Serial No. 72,205.

This invention relates. to improvements in a process for producing asphaltic road material, and refer's more particularly to'a proc- 'ess by means of which a material is produced which may be easily worked and is of a slushy consistency when laid and is further adapted to be laid cold, producing a compact non-rolling pavement.

Among'further objectsof the invention are, to provide a process for making wasphaltiemix adaptable for use both in the base and binder course and by varying the size of the aggregate it may be as well used in top course and surfacing for patchwork or generally in the road making art. The invention consists primarily in the combination or incorporatlon of an as haltic binder intimately bonded with a crus ed stone aggregate, the stone having been first dried to produce a better adhesion between the binder material and the mineral matter and a solvent or relatively light hydrocarbon .beingmixed with the asphaltic binder prior to its combination with the mineral aggregate to increase the fluidity of the binder and pro duce a' mix which may be .worked cold and shipped for considerable distances without setting or becaming congealed to'the extent that it is difficult to remove the same from open-topped cars.

This invention is a continuation in part of a'prior application Serial No. 39,815, filed June 26,1925.

The process of combining an 'asphaltic' binder with a mineral aggregate to form an asnhaltic concrete is well known in the art. Furthermore, it is a well known practice to heat the mineral aggregate to drive ofi moisture contained therein, this moisture having the effect of preventing the proper contact and adhesion between the mineral aggregate and the asphalt. Furthermore, it is common practice to use a solvent or a relatively light fluid hydrocarbon which is com- '-bined with the stone and which is described as having the particular advantageous prop erties, not only in reducing the fluidity of the hydrocarbon binder, but also in its ability to produce a better adhesion between the mineral-aggregate and binder. Furthermore, in

some 1nstances it has been contended that .there is a certain amount of saponification produced. This particular phase of the prior art 'is, however, somewhat doubtful.

recognizing the} prior art, particular attention'has been givenv to the Amies patents;

The novelty and improvement in the pres-- ent invention as "distinguished from this prior art lies, however, in the fact that it has been found that by fi'rstcombining the sol-.

vent orlight hydrocarbon with the asphalt instead ofmixing the solvent with the stone, much better results in the final product and a much better mix from every stand oint is produced. Furthermore,it has been 'ound an advantage to remove from the crushed stone aggregate what is termed as the fines or the smaller granular particles comprising primarily an-impalpable dust which, if permitted to remain and form a art of the mix, facilitates. the movement of the pavement when laid, producing rolling and reventing to a great extent the rigid inter ocking of the angular surfaces of the crushed stone.

The single figure is a side diagrammatic View of ,an apparatus for heating the aggregate to remoye the moisture with a blower connection for eliminating the fines from the aggregate.

o nions. The trunnions are in turn supported by suitable standards 3. Four (4) is a hopper, the discharge end of which is connected to a chute 5,-the latter inserted in the end of the retort by means of which the aggregate is introduced; 6 is a burner fuel, which may be either gas or oil,-inserte'd in-the end of the retort and receiving its air supply either directly from the atmosphere or through the duct 7 which has communication with the dust separator or arrester 8; 9 is a blower fan adapted to force a current of air through the perforations 10 in the clean air passes in a course shown by the arrows into the top of the duct 7 and thence back into the'retort, or it may be exhausted through an auxiliary line 12 controlled by a damper 13. Over the open disch rge end of the retort is held in place m stationary bafile 14: covering the greater part of the .discharge end of the retort and preventing s'hort-circuiting of the air discharged from the blower fan 9 through the holes of the retort. This baffle element causes the dust is a retort rotatable upon the trunladen air to pass into the duct 11 and thence 'into the dust arrester in place of being discharged through the end of the retort. The lower portion of the element 14 is cut away to permit the aggregate to pass into a storage bin or the boot of an elevator not shown.

In operation, the mineral aggregate is introduced to the hopper 4 from any convenient source and is thence charged to the rotating retort 1 where it issubjected to the rolling and tumbling action of the retort in its rotation accompanied by additional mixing action produced by obstructions or ribs 15 positioned above the interior of the retort. This rotating retort is preferably inclined towards its discharge end so that the stone aggregate works along, while during this rotation of the aggregate and mixture,

" 500? F. or more are sufficient.

there is introduced to the retort heat supplied by means of. the burner 6. The temperature on the interior of the retort is controlled to eliminate any moisture contained in the stone. Normally, temperatures of The retort is supported, as described, by means of the trunnion bearings 2 while rotative motion is imparted by means of a driving gear 16 meshing with a girth gear 17 attached .to the periphery of the retort. The driving gear is mounted upon a shaft 18 which is driven from any suitable source of power by means of the pulley 19. Y

The stone aggregate introduced to the hopper 4 is first properly graded to contain the proper percentage of mineral matter of the size best adapted to the purposes to which the agregate is to be used. On discharge from the retort, and after elimination of the fines, this mineral aggregatewhich may consist of crusher-run stone, either limestone, granite, crushed gravel or other adaptable mineral matter-is in condition to be combined with the binder in a suitable mixer such as a pug mill. Normally, for the binder course, stone ranging from one 7 and one-fourth inches to onefourth inch, properly graded, is satisfactory. For thetop course or surfacing, the mineral aggregate'must be graded accordingly with a greater percentage of the smaller stone.

The asphalt specifications will vary with climatic conditions. Through the'South, 'asphalt penetration will range from '60 to 70,- while in the North. penetration is considerably greater,.in the vicinity of 95. The ductihty, in any cases, should not be materially under 85 at77 F. The asphaltic material may be either naturalasphalt or a petroleum residue,--the latter being more commonlyutilized at the present time due its cheapness and-better adaptibility to body t'oa liquid con this type of mixture.

The asphalt is pre ared by heating in a 'tion.. The solvent is then introducedato the-asphaltic body by may be added through ahollow stirring v dc-'- vice through which the solvent flows and is introduced by being discharged. into the bottom of the asphaltic body fromthe end of the stirring device or separate mechanical agitators may be used to keep the asphaltic body in agitation while the solvent or light hydrocarbon is introduced through a perforated pipe seated in the bottom of the mixer, the perforations being so arranged that the solvent is evenly distributed throughout. T he asphalt is normally heated to temperature ranges of 250 to 325 F the temperatures depending primarily upon the character of the asphalt and the nature of the solvent, it being understood that the asphalt should not be heated above the flash relatively volatile solvent is used, the temperatures should be considerably lower than when a solvent of a less volatile character is tobe combined With the asphalt. The nature of the solvent will depend primarily upon the distance the mix is to be transported before laying. Such light hydrocarbons as naphtha, kerosene, benzine, or similar unrefined relatively volatile products, are used. After the solvent has been thoroughly incorporated into the asphalt, increasing materially its fluidity to a degree that it may be readily combined and intimately mixed with the aggregate, there is also added a filler material such as pulverized slate, shale, lime stone dust or hydraulic cement. This filler has the quality of maintaining the asphalt in a relatively solid condition after'it has been laid or set upon the road. Even should the pavement be subjected to relatively high temperatures, which normalfly' would produce flowing of the asphaltic bin er, the filler material keeps the asphalt m a bonded condition by supplying tiny granular particles which serve to bond the asphalt into a unitary mass. The mixture of asphaltic binder, solvent and filler material,

which we may consider as our binder mix, is

of the binder substance and, as-a consequence,

the complete bond acquired by the present. fpllrlocess was notpossible. Furthermore, the or material was heretofore added during primarily in the combination of the binder and tending to limit the distribution of the filler to concentrated areas oftheaggregate. The

combining it with the binder mix before mixing the binder with the aggregate elimi-' nates the difliculty of isolating the-filler ma- .terial to concentrated regions in the aggre'-.

gate.

As mentioned heretofore, the elimination of the fines or dust :Erom'v the aggregate ieliminates an impalpable powder which heretofore has had the effect of preventing complete adhesion-betweenthe asphalt and stoneaggregate,in fact, the powder acts as; :a glaze which the asphaltic binder was unable. 'to penetrate. Furthermore, the fines present? employ" practice of adding the filler and intimately the crushed- V I I clalm as my invention:

-1. Aprocess of making asphaltic road material, comprislng' the steps of properly grading a mineral aggregate, heating the same to dryness,--separately heating an as phaltic binder and adding a hydrocarbon solvent to increaseits fluidity, incorporating into the asphalt mix while hot a filler comprising an' argillaceous material 4 and intimately combining the final asphaltic mixture 1 with the dried mineral aggregate.

2. A process, such as that described 'in claim 1, in which. the filler material consists of hydraulic cement. I

3. A, process; such as that described in clai'ln 1 in which the filler material constitutesnot less'fth'an one-half'percent or more than one mix. 1 I 4 -4. A'process', such as that described in claini 1, in which the solvent is added tothe.

asphaltic binder by introducing theformer under ressure. into the'bottom of the-asphaL ticboy.

p l ifo the total weight of the onas. FoiinEsTEai 

